Energy sensitive direct conversion radiation detector

Abstract

An x-ray detector capable of directly converting x-ray radiation into electrical signals utilizes the radiation induced conductivity of various solid, electrically insulating materials. The detector is configured comprising one or more anodes and cathodes separated by various thicknesses of dielectric material wherein ionization occurs primarily in the electrodes of such detector structure. The radiation induced conductivity of the dielectric material can be modulated by controlling the size, orientation and composition of the electrodes and the dielectric materials as well as the electrical bias between anode and cathode.

1. A direct conversion radiation detector, comprising:
 at least two electrode plates orientated parallel to each other defining a set of electrode plates wherein for each set of electrode plates a first plate is a cathode comprising a material possessing an element with an atomic number≧26, and wherein a second plate is an anode; and 
 a dielectric material interposed between the at least two electrode plates wherein absorption of ionizing radiation of a particular energy range by at least one of the at least two electrode plates produces secondary ionization in the dielectric material resulting in radiation induced conductivity of the dielectric material creating a measurable electric current when an external voltage is imposed between the anode and the cathode. 
 
     
     
       2. The direct conversion radiation detector of  claim 1  wherein the ionizing radiation comprises x-rays. 
     
     
       3. The direct conversion radiation detector of  claim 1  wherein energetic charged particle(s) produced by absorption or inelastic scattering of x-rays in the set of electrode plates can escape said set of electrode plates producing ionization in the dielectric material. 
     
     
       4. The direct conversion radiation detector of  claim 1  wherein a minimum thickness of the dielectric material is equal to or larger than a continuous slowing down approximation range of energetic charged particle(s) in the dielectric material, said energetic charged particle(s) having been produced by absorption or inelastic scattering of an x-ray in either the cathode or the anode. 
     
     
       5. The direct conversion radiation detector of  claim 1  wherein the anode and the cathode comprise material that is identical. 
     
     
       6. The direct conversion radiation detector of  claim 1  wherein the dielectric material comprising a material possessing an element with an atomic number≧26, including lead, tellurium, or gadolinium. 
     
     
       7. The direct conversion radiation detector of  claim 1  further comprising a third electrode plate wherein the third plate is a cathode positioned parallel with respect to the first plate and the second plate so as to place the first plate between the second plate and the third plate, and wherein the dielectric material is interposed between the first plate and the second plate and between the first plate and the third plate. 
     
     
       8. The direct conversion radiation detector of  claim 1  wherein each set of electrode plates is orientated normal to the incident ionizing radiation. 
     
     
       9. The direct conversion radiation detector of  claim 8  wherein a plurality of sets of electrode plates are configured adjacent to one another normal to an incident ionizing radiation beam and wherein anode and/or cathode thickness and dielectric material thickness of each successive set of electrode plates is larger than previous sets of electrode plates. 
     
     
       10. The direct conversion radiation detector of  claim 8  wherein the at least two electrode plates are flat plate electrodes and wherein a plurality of detector pixels are defined by a septum formed by parallel pairs of the flat plate electrodes, said flat plate electrodes being perpendicular to the anodes and cathodes, and wherein the dielectric material is interposed between said pairs of such flat plate electrodes, said electrodes being biased to a single electrical potential such that current flow between any two such flat plate electrodes is prevented. 
     
     
       11. The direct conversion radiation detector of  claim 10  wherein the flat plate electrodes defining the septum between pixels are biased to an anode potential, and wherein an anode oriented perpendicular to said electrode plates is adjacent to said electrode plates, and wherein a region adjacent to such electrode plates defining the septa is void of a cathode. 
     
     
       12. The direct conversion radiation detector of  claim 8  wherein the detector comprises a plurality of layers of sets of electrode plates, each layer being parallel to an incident ionization beam and each set within each layer being offset in a direction normal to the incident ionization radiation. 
     
     
       13. The direct conversion radiation detector of  claim 1  wherein radiation energies for the particular energy range are from approximately 1 keV to approximately 200 keV. 
     
     
       14. The direct conversion radiation detector of  claim 1  wherein each set of electrode plates is orientated parallel to incident ionizing radiation. 
     
     
       15. The direct conversion radiation detector of  claim 1  wherein a maximum thickness of the cathode or anode is less than a continuous slowing down approximation range of charged particle(s) produced by absorption or inelastic scattering of an x-ray of the particular energy range in the cathode or anode. 
     
     
       16. The direct conversion radiation detector of  claim 1  wherein at least one of the at least two electrode plates is a flat plate configured with a plurality of polyhedron adjacent to said flat plate, said plurality of polyhedron having a composition identical to said flat plate composition, wherein said polyhedra is arranged in an array such that there is a gap between any two polyhedra, said gap filled with dielectric material. 
     
     
       17. The direct conversion radiation detector of  claim 16  wherein both the cathode and the anode are configured with said plurality of polyhedra, and wherein orientation of the anode with respect to the cathode is such that the plurality of polyhedra adjacent to the anode are interdigitated with the plurality of polyhedra adjacent to the cathode, and wherein the space between the cathode, or any polyhedron adjacent to the cathode, and the anode, or any polyhedron adjacent to the anode, is filled with dielectric material. 
     
     
       18. The direct conversion radiation detector of  claim 17  wherein the plurality of polyhedra adjacent to both anode and cathode are of a shape chosen from a list consisting of rectangular parallelpiped, pyramid and prism. 
     
     
       19. The direct conversion radiation detector of  claim 17  wherein the plurality of polyhera adjacent to both cathode and anode are replaced with a plurality of either a right circular cone or right circular cylinder. 
     
     
       20. A method for converting ionizing radiation directly to an electrical current, the method comprising:
 configuring at least two electrode plates parallel to each other defining a set of electrode plates wherein for each set of electrode plates a first plate is a cathode comprising a material possessing an element with an atomic number≧26 and a second plate is an anode; 
 separating the at least two electrode plates with a dielectric material; and 
 producing secondary ionization in the dielectric material by absorbing x-ray radiation of a particular energy range in at least one of the at least two electrode plates, wherein a charged particle(s) resulting from absorption or inelastic scattering of x-ray radiation produces secondary ionization in the dielectric resulting in radiation induced conductivity of said dielectric material, and wherein a measurable electric current is produced when an external voltage is imposed between the anode and the cathode. 
 
     
     
       21. The method for converting ionizing radiation directly to an electrical current of  claim 20  wherein a thickness of either the cathode and/or anode produces energetic charged particle(s) in the detector by absorption or inelastic scattering of x-rays in the set of electrode plates of the detector, and wherein said energetic charged particle(s) escape said set of electrode plates producing ionization in the dielectric material. 
     
     
       22. The method for converting ionizing radiation directly to an electrical current of  claim 20  wherein a minimum thickness of the dielectric material is equal to or larger than a maximum continuous slowing down approximation range of energetic charged particle(s) produced by absorption or inelastic scattering of an x-ray in either the cathode or the anode in the dielectric material. 
     
     
       23. The method for converting ionizing radiation directly to an electrical current of  claim 20  further comprising orientating a plurality of sets of electrode plates configured adjacent to one another normal to an incident radiation beam and wherein anode and/or cathode thickness and dielectric material thickness of each successive set of electrode plates is larger than previous sets of electrode plates. 
     
     
       24. The method for converting ionizing radiation directly to an electrical current of  claim 20  further comprising orientating a plurality of layers of sets of electrode plates, each layer being parallel to an incident radiation beam and wherein each set of electrode plates is offset in a direction normal to the incident radiation beam.